DFG Interface Contract for RBIT and NAT

This document defines the formal interface contract between Resolution-Based Information Theory (RBIT, Series I) and Network Architecture Theory (NAT, Series II) within the Deficit-Fractal Governance (DFG) framework. It specifies four interfaces that bind the two theories into a single coherent architecture with a strict one-directional dependency: RBIT → NAT. The four interfaces are: (I1) Resolution Gap as Routing Invariant — NAT's data classification is a routing function of RBIT's Δρ sign, preserving the error asymmetry where under-escalation is dangerous and over-escalation is merely costly; (I2) Structural Diversity as Detection Precondition — RBIT's upscaling cycle creates empty space vulnerable to corruption, and NAT specifies architectural diversity as the mathematical precondition for detection; (I3) Spectral Gap as Storm Governance Parameter — the sphere topology's mixing time determines whether local resolution failures become systemic storms; (I4) Triple Concordance as Shared Detection Protocol — combining RBIT's R-ρ-f_esc concordance with NAT's structural diversity to detect Self-Consistent Misalignment. The contract serves as a locked shared reference: neither companion paper re-derives the other's results, and all cross-theory dependencies are routed through these four interfaces.